Optical Application Specific Integrated Circuits (OASICs) are integrated circuits which operate on light to perform one or more functions. OASICs are optical waveguides which contain optical paths for light to travel in and optical operators which operate on the light to perform specific functions. Such operations include, for example, splitting light so that light on one optical path is split onto several optical paths. In this case, the light in each optical path carries the same information but at a lower power level than the power level of the light before it was split. Optical combiners operate on light to combine light from several optical paths into one optical path. Another type of operation performed by OASICs is wavelength division multiplexing (WDM) wherein light comprising a plurality of wavelengths traveling along one optical path is operated on to spatially separate light of different wavelengths. WDM allows information to be sent on one optical fiber at different frequencies and to be separated out by frequency by the OASIC into spatially separated optical paths.
OASICs have input ports which are intended to be coupled to incoming optical fibers for receiving light therefrom and output ports which are intended to be coupled to outgoing optical fibers for outputting light thereto after it has been operated on by the OASIC. It is often desirable to connect the OASIC to several optical fiber cables. For example, it is often desirable to connect the OASIC to one optical fiber cable coming from the central office and to another optical fiber cable coming from the subscriber's premises. Each of the optical fiber cables normally contain many optical fibers. Rather than connect the fibers from the cables directly to the OASIC in the field, optical fiber ribbons normally are connectorized, or terminated, to the OASIC in the plant so that they are sold to customers with an optical fiber ribbon connected to each side of the OASIC. The optical fibers from the cables are then optically coupled to the appropriate port of the OASIC by splicing certain optical fibers from the cables with certain optical fibers from the ribbon connected to the OASIC. This may be accomplished by, for example, single-fiber fusion splicing, which normally requires breaking out individual fibers from the ribbons and splicing them with individual fibers from the cables.
In order to maximize the density or number of circuits on an OASIC substrate, they generally are not designed with all of the ports to be connected to one cable or ribbon on one side of the chip and all of the ports to be connected to another cable or ribbon on the other side of the chip. This is because the optical paths cannot bend beyond a certain amount without attenuating the optical signal and also because of limits on crossovers of waveguides within the OASIC. Therefore, ports to be connected to fibers from each cable or ribbon generally are located on both sides of the chip. As a result, some of the fibers of a given ribbon connected to the OASIC will have to be spliced with fibers from one cable or ribbon while other fibers of the same ribbon connected to the OASIC will have to be spliced with fibers from the other cable or ribbon. The result is that the splicing task is difficult to perform and prone to human error because it requires breaking out and splicing of individual fibers. Therefore, this type of arrangement is not suitable for interconnection of mass optical fiber connections by mass splicing (e.g., the splicing of one fiber ribbon with another fiber ribbon by mass fusion splicing) because the optical fibers connected to the ports of the OASIC are not arranged to facilitate mass splicing.
Accordingly, a need exists for method and apparatus for interfacing optical fibers from optical fiber cables and ribbons with optical integrated circuits which allows the fibers of the cables or ribbons to be easily coupled to the fibers connected to the optical integrated circuit by using mass joining techniques such as mass fusion splicing, mass mechanical splicing or mass connectorization.